How to control steel structure welding deformation

In the construction of steel structure engineering, the welding deformation directly affects the installation and use functions of steel components and steel structures. And the additional bending moment, secondary stress, etc. generated during the load will indirectly affect the performance of the steel structure engineering, so the control of welding deformation is very important.



According to the causes and influencing factors of welding deformation, the following misplaced control deformation can be adopted:

1. Reduce the cross-sectional area of the weld: Under the premise of obtaining a good weld without excessive defects, use the smaller groove size (angle and clearance) as much as possible.

2. For the yield strength below 345 MPa, the steel with weak hardenability is less heat input, and the preheating and interlaminar temperature are not preheated as much as possible: the heat transfer is less preferred, such as CO2 gas. Protective welding.

3. Thick plate welding should use multilayer welding instead of single layer welding.

4. In the case of meeting the design requirements, the longitudinal reinforcement plate and the transverse stiffeners may be welded by intermittent welding.

5. When both sides can be welded, double-sided symmetrical groove should be used, and in the multi-layer welding, the welding sequence with the axis neutrality of the member should be adopted.

6. When the T-joint plate is thick, the bevel joint is used for the butt joint.

7. Use the pre-weld reverse deformation method to control the angular deformation after welding.

8. Control the post-weld deformation by rigid fixture fixing method.

9. The length of the weld is compensated by the length of the component. For example, the longitudinal weld of the H-beam can be reserved for 0.5mm-0.7mm per meter length, and the length of the corresponding steel for each pair of transverse bars can be reserved for 0.5mm. The longitudinal and transverse shrinkage deformation of the weld of the cylindrical pipe member is compensated. If the plate thickness is greater than 10 mm, a circumference of 2.0 mm is reserved for each longitudinal and circumferential weld.

10. For the distortion of long members, it is mainly to improve the flatness of the plate and the assembly precision of the components, so that the groove angle and the gap are accurate, and the arc pointing or centering is accurate, so that the weld angle is deformed and the longitudinal deformation values of the wing and the web are obtained. Consistent along the length of the member.

11. The design should minimize the number and size of the welds; if the welds are properly arranged, in addition to avoiding the welds, the welds should be placed as close as possible to the neutral axis of the members, and the welds should be arranged and constructed. The neutralization axis is symmetrical.

12. When welding many components of the weld joint or when installing the steel structure, a reasonable welding sequence should be adopted.

Welding deformation control and correction

Improved welding design -

(1) Minimize the number of welds

When designing the weld structure, unnecessary welds should be avoided. Steels and stampings should be used instead of welded parts to reduce the number of ribs to reduce the amount of welding and correcting deformation.

(2) Reasonable selection of weld shape and size

For a larger part of the butt joint, the X-shaped groove should be selected instead of the V-shaped groove. Reduce the total amount of deposited metal to reduce weld distortion. Smaller weld sizes should be used wherever possible to ensure adequate capacity. For T-joints that do not require strength calculations, a process-optimal minimum fillet size should be used. And the use of intermittent welds can reduce deformation more than continuous welds.

When the T-joint fillet weld is determined by design calculation, continuous weld seam shall be used, and the same intermittent weld shall not be used, and double-sided continuous weld shall be used instead of equal-strength single-sided continuous weld. To reduce the weld angle size.

For T-shaped or cross-connected joints with large force, under the condition of ensuring the same strength, fillet welds with broken joints should be used, which can greatly reduce weld metal and reduce weld deformation than general fillet welds.



(3) Reasonable design of structural form and weld location

When designing the structure, the minimum amount of welding work and the minimum amount of welding deformation during component assembly should be considered. For thin plate structures, the appropriate plate thickness, frame spacing and weld angle should be selected to improve structural stability and reduce wave deformation. In addition, you should try to avoid designing curved structures. Because the flat surface can make the welding equipment in a fixed state relatively simple, it is easy to control the welding deformation.

Since the transverse shrinkage of the weld is usually more pronounced than the longitudinal shrinkage, the weld should be placed as far as possible in the direction parallel to the minimum amount of weld deformation required. The position of the weld should be as close as possible to the central axis of the section and as symmetrical as possible to the central axis to reduce the bending deformation of the structure.

                                                                                                                                         - From Welding Technology